Under the development of the long term evolution (LTE) by the third generation partnership project (3GPP), broadcasting of user data, such as IP-TV, is currently being planned. Multimedia broadcast/multicast services (MBMS) is the technique envisioned for the broadcasting services in LTE.
The actors within the field of national security and public safety (NSPS) are engaged in a constant strive to protect the society and its citizens against attacks and dangers of various forms. The national security refers to the protection of the society against any form of attack. Public safety refers to the protection of the society from all types of harm, danger, injury or damage and is provided by emergency services, such as the police, the fire brigade etc. Reliable communication and information supply are critical for the success of a mission. Public safety organizations are, therefore, particularly interested in group communications, i.e. group calls, and dedicated resources are being provided for these organizations.
For national security and public safety (NSPS), a product release for LTE may be based on unicast, i.e. every participant in a group call, in addition to its default bearer, will get a dedicated channel to carry voice. A guaranteed bit rate (GBR) bearer is assumed to be allocated as dedicated bearer for each member participating in the group call. The current assumption is that it shall be possible to support at least 100 simultaneous users per cell on a 5 MHz bearer. For future product releases, the MBMS multicast mode would be a natural choice for NSPS group calls. In the MBMS multicast mode, the user subscribes to the multicast service and land charging data for the end user may be generated.
For scenarios where the participants in a group call tend to cluster, e.g. at the scene of some major fire or other accident, the number of users in one cell may exceed the capacity of an NSPS system based on unicast. To handle those scenarios, a broadcast solution would be needed. As stated above, MBMS is being standardized and it will take considerable time before MBMS capable user equipments (UEs) reach the market. There is, therefore, a need for a solution which overcomes at least one of the above-mentioned drawbacks.